1. Field of the Invention
The present invention relates to a liquid discharge recording head (also referred to merely as “recording head” hereinafter) for forming an image on a surface of a recording medium by discharging ink or other liquid toward the recording medium and a method for manufacturing such a head. Here, the wording “form an image” means that not only any meaningful image such as a character, a figure, a symbol or the like is formed, but also a particular meaningless image such as a geometric pattern or the like is formed.
2. Related Background Art
In conventional recording heads, liquid is supplied to a plurality of flow paths formed in one surface of a substrate via liquid supply ports extending through the substrate in a thickness-wise direction, and the liquid is supplied to corresponding discharge ports via the respective flow paths. In general, the flow paths and the discharge ports are formed by patterning of a film made of organic resin material and formed on one surface of the substrate. The reason is that, although the film is required to have a thickness of several μm to several tens of μm, the organic resin material is suitable to obtain such a thick film cheaply in a mass production.
However, the organic resin material has properties such as low mechanical strength, a low glass transition point, high thermal expansion rate and high moisture absorption expansion rate, and thus, due to such properties, there arise a problem that endurance and reliability of the recording head are reduced.
However, the organic resin material has properties such as low mechanical strength, a low glass transition point, high thermal expansion rate and high moisture absorption expansion rate, and thus, due to such properties, there arises a problem that endurance and reliability of the recording head are reduced.
To cope with this, as disclosed in Japanese Patent Application Laid-Open No. 2001-287373, there have been proposed a recording head and a method for manufacturing such a head, in which flow paths and discharge ports are formed by using inorganic material. Now, the method for manufacturing the recording head disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2001-287373 will be described with reference to FIGS. 4A, 4B, 4C, 4D, 4E and 4F. First of all, as shown in FIG. 4A, a heat-insulative layer 31, a heating layer 32, a protective layer 33 and an anti-cavitation layer 34 are laminated, in order, on a surface of a silicon substrate 30. Then, as shown in FIG. 4B, a pattern layer 35 corresponding to a desired flow path configuration is laminated. Thereafter, as shown in FIG. 4C, an inorganic material layer 36 for forming flow paths and discharge ports is laminated on the pattern layer 35. Thereafter, as shown in FIG. 4D, the formed inorganic material layer 36 is flattened by CMP (chemical mechanical planarization). Then, as shown in FIG. 4E, after a water-repellent layer is formed on a surface of the flattened inorganic material layer 36, a pattern image having a desired discharge port configuration is illuminated by a femto second laser, thereby piercing the discharge ports 38. In this way, a nozzle plate 39 is formed on the silicon substrate 30. Thereafter, as shown in FIG. 4F, the silicon substrate 30 is subjected to etching from its back surface side to form liquid supply ports 40, and the flow paths 41 are formed by removing the pattern layer 35 from the formed liquid supply ports 40.
However, the manufacturing method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2001-287373 had the following problems. That is to say, in consideration of flattening treatment in post-processing, the inorganic material layer having considerable thickness must be stacked. For example, in a case where the thickness (height) of the pattern layer is 5 μm, the inorganic material layer having a thickness of about 15 μm must be stacked. Thus, the through-put of the film forming apparatus is considerably worsened, so that the mass production is hard to be achieved unless many of expensive film forming apparatuses are provided. Further, in a case where a high density arrangement of nozzles is further developed, with the result that a gap between the pattern layers is more reduced, filling of the inorganic material into the gap is worsened. As a result, there is a great possibility of generating voids in the nozzle plate. If any void is created in the nozzle plate, the strength and reliability of the nozzle plate will be reduced. On the other hand, if any void is tried to be prevented from being created in the nozzle plate, the degree of freedom for the designing will be greatly limited. Further, the greater the thickness of the inorganic material layer, the greater inner stress, with the result that breakage is apt to be occurred in an interface between the layer and the silicon substrate. Generally, the conventional manufacturing methods are expensive and have low through-put.